A lot depends - for a grid tie system with high time of day usage in summer it probably does if you have the room. In some areas rates can vary as much as 500%+ between off hours and max power usage hours.

At one time it was worth it in almost all applications, because solar panels were in the $7-10 per watt range. But when panels dropped to under $5 per watt, it usually was not worth it. But lately more and more utility companies are forcing people to some kind of variable rate structure, which in some cases can be as high as 75 cents per KWH in the noonish to sundown time frame.

More panels beats tracking in all ways except one, if you don't have the space for the extra panels then maybe a tracker might be a solution. But frankly if you have space for a tracker its hard to imagine you couldn't have more panels

Tracking doesn't give 30-40% improvement year round, summer is best with long days and larger arc of the sun ... but that typically not when offgrid needs extra power as typically they design for worst case which in the cold, short winter months

With panels now well under 3 bucks a watt, its cheaper, no maintenance and year round power improvement to have more panels than less with a tracker.

Tracking doesn't give 30-40% improvement year round, summer is best with long days and larger arc of the sun ... but that typically not when offgrid needs extra power as typically they design for worst case which in the cold, short winter months

Tracking is great when the system works and is fascinating to watch. I have a parabolic dish that tracks for a DHW show and tell. I have had enough of the glitches that come with mechanical tracking components. It is inop now, (needs new brushes) and will be glad to take it down soon for good. Fixed panels are almost no maintenance, and a small percentage more in panels needed to account for 'fixed' is well worth it in the long run.

It's always getting out of whack with the brushes in the linear actuators - especially the azimuth actuator, blown fuses, etc... The mechanical problems to me are not worth the gain. I'm sure if one factored in the cost for maintenance and repair, the gain in harvest would be offset by repairs and down time.

Tracking offgrid is the number one way if your location supports it to get completely away from generator use. This goal is very hard to do on a reasonable budget but a tracker is the path. I can not tell you the absolute difference other than we went from 25 days our batteries did not complete charge down to 5 per year. The other feature is you are off battery power earlier in the day and can do more with a smaller battery system. Conversely you can run cooling in summer at 7pm long after the fixed array has gone to sleep.

There just are too many variables but I would tell you a 2KW or slightly less tracker will do for most couples what 4KW fixed would do in winter up here in the Sierra. Winter is where the design is done and since all I do is trackers now it is my business model. I do not want phone calls!!! From my experience there just are too many days when an hour of sunlight at 9 am and another hour at 2 pm happen in winter. There are other senarios of clouds and just plain weather that a tracked array is superior over fixed.

If you like cold starting generators in the snow/ dealing with surges, doing alot more maintenance, having a big footprint of panels to deal with, a fixed array is definately for you. I do like a fixed array with a tracker so I am reasonable! I probably would agree with most of the gridtie folks here except I tried it. Definately no going back!

I agree that tracking systems need lots of maintenance... Anything electro-mechanical outside in the weather just does.

4-5 years ago, when I first looked into Grid Tied Solar--I went to a famous RE Store out here (Real Goods Solar Inc). They had a whole bunch of different arrays on their property. The only ones obviously not working where the 2-axis trackers (3 of them--all weathered and probably year(s?) old). They where pointing away from the sun, an actuator hanging by one anchor point, etc. If a solar store could not bother with keeping them running--why would one of their customers try.

But, if you are interested in a tracker, doing the back of the envelope calculations is worth the trouble.

I don't remember if you said where you are located, but assume near Springfield Illinois. And use the PV Watts Website Program to compare various options (orientation, panel size, fixed, 1 or 2 axis tracking, etc.). The PV Watts program does include ~20 years of averaged weather too...

Pick 1kW of solar panel, one with optimum fixed mount, the other with full 2-axis tracking. Assume 0.52 Derating (total end to end efficiency: solar panel rating to 120 VAC out the inverter, flooded cell batteries).

So, for deep winter use in Illinois, a 1kW off-grid system will require ~2-5 gallons per December to make up for the lack of 2-axis tracking. Depending on your needs (full time living vs seasonal usage, A/C or fans for summer use, etc.)--you can look at the numbers that will reflect your lifestyle.

There are many ways of looking at the problem--and some you may choose just because it reflects your personal choices.

Cost wise--I would be surprised if a full off grid system (tracking or fixed mount) would be cheaper per kWhr vs paying the utility to run a drop to your home and installing a fixed Grid Tied array--possibly a hybrid system (like the Xantrex XW system) if you have lots of power interruptions (such as ice storms and it takes weeks to get power restored). Also, many of the local rebates require you to be grid tied to qualify for government funding of your installation (www.dsireusa.org).

You can also look at what your grid costs would be. Guess that your power company wants to charge you $20,000 to run power 600' to your home. You use a minimum amount of power (efficient but full use of power) at 300 kWhrs per month. And that you will spread the payback over 20 years (no interest):

In the end, Grid Tied solar will cost you around $0.10-$0.30 per kWhr. And Off Grid solar will cost you around $1.00-$2.00+ per kWhr (including extra losses due to batteries and inverters, storage batteries and their replacement costs ever ~10 years). A hybrid system (Xantrex XW type) will be somewhere in between.

I agree that tracking systems need lots of maintenance... Anything electro-mechanical outside in the weather just does.

-Bill

This has not been my experience. I suppose on homebrew trackers this would be true. Of coarse Bill, it is alot of work squeezing a grease gun 5 or 6 times twice a year! You do have to have the stamina! The 5 trackers up here that I hang my hat on have a combined total of 22 years without problems.

Of coarse one of the units could fail and the worst thing about that would be it is now a fixed mount......................................

In my Off Grid system, we evaluated manual versus tracking racks and decided it was pretty expensive given 40 panels. I was uneasy about tracking reliability/maintenance and opted for more panels.

If I remember right my back of the enevelope calc resulted in extra panels being cheaper than setting up trackers (civil/hardware) and factoring in a couple of failures over time. If you're running fewer panels and are located in a part of the country where you need to compensate for less sun power they might make sense.

For a number of reasons, I made the decision to accept the cost of building some charging overcapacity into the system.

Based on actual experience with the fixed array set up, I have abandoned repositioning the array twice a year as the panel capacity is able to handle the winter charging slack in only one position with a little help from the genny once in awhile.

Hey Arizona!
Almost ended up in Arizona myself! Beautiful state. You are in on of the best places in the world for solar. Question are you running a generator for your system? The reason I ask is for me the tracked array and a fixed was the key to making the generator go to someone elses house. I have client who just unloaded 1600 watts from the roof and is amazed at how much power he has late in the day tracking during summer. I am guessing eastern Arizona?? White mountains??

Engineers would not install anything else. They said the 1800 RPM units last much longer are quieter and use less fuel. It is a little larger than I needed but at higher altitudes KW output is derated.

The only service we do are oil changes. They make the industrial units in smaller KWs' too. It only runs 60-80 hours a year including weekly tests but mandatory for peace of mind especially in remote areas like ours.

Agree with your comments and I too have customers like you.
The other side of the coin is I have customers (including myself) who do not want, need, or desire to run a generator and a tracked array is the only way to get there in my opinion. Climates like yours make it very hard to run without a generator but I believe now with the inverter based DC compressor's and high SEER's that even in your neck of the woods it could be done. The key to do this is running a smaller Btu compressor at first light (7am Tracked) and running it all day (7pm Tracked) Just about impossible for a fixed array to get decent power levels at the extremes of the solar day.

There also is peace of mind in this approach as the only day you have to be concerned with is when the sun does not shine for 2 hours. In both our necks of the woods that happens less that 10 days a year with a tracker.

There are always other factors and each home has it's requirements. I really love remote homes and I have them in spades. Some amazing friendships over the years and very similar to my years off cruising the tropics in a sailboat. Just Fun and a ton of work. I think it is the quietness of these special remote places that can drop the jaws of city dwellers. No need to mention the stars last night!

Dan
Nice job, well documented. I built my tracker 2 years ago and if I didn't know better I would think you copied mine. About the only thing I did differently is that I used 1.5" solid steel bar stock and pillow block bearings for the inclinattion and east west axis pivot points. The only problems I have had is with the linear actuator, the limit sw. failed so the actuator went to its stop and then tore up the internal plastic gears. I had a spare so no down time. I would love to find a deal on a good actuator like you did. I also used a second linear actuator to control the inlination angle, it also allows me to lay the panels flat with just the flip of a switch in really high winds. I also used the sensor from Redroc, could not be happier. I used to make underwater camera housings, so making a weather tite housing for the little circuit board was a no brainer.
Anyways, thanks for sharing, it looks like you had as much fun as I did in building it.
Larry

I also built a pair of single axis homemade trackers.....about 600 bucks each.

I'm using Analoguy.com for the actuator controller. One controller operates both arrays using a set of relays off the circuit board output.

Mine consists of an "H" made of 1.5" square tubing ( black in the photo ) welded to a pc of 2" round shaft steel that runs thru 2 pillow block greasable bearings bolted to a pc of 8" channel, which is welded at laditude angle to a 6" steel pole. The panels mount to unistrut that is bolted to the square tubing. A 36" actuator operates the rack.

Feel free to use what ever you want - that's one reason that I post detailed info on the build.

RP/TN,

Due to my altitude and severe weather that we can get I did not want to use any pillow blocks, and by using delrin - never need to have to grease them!!

The polar mount is certainly nothing new and easy to build. By using the round collars over the post I did not have to take care in how the post (and any predrilling) was positioned in the concrete. This way all can be done after the post is set into the concrete.

I guess I am missing something. This sounds much like the Intermatic ST01 which is a sun timer. You still have to input something to drive the motor and you need feedback to know that it is where it is suppose to be. Most of the motors are 24VDC so are you saying you would just program it for every 15 minutes of the day?

I did not see a rating for contact voltages. The Intermatic has a 35vdc rating and I use it for exterior lighting. How would you control 2 axis?

I am pulling for you on this one! There was a company last year that was going to do this for portable and RV but the recession killed it. Good luck!!!!!

I guess I am missing something. This sounds much like the Intermatic ST01 which is a sun timer. You still have to input something to drive the motor and you need feedback to know that it is where it is suppose to be. Most of the motors are 24VDC so are you saying you would just program it for every 15 minutes of the day?

Not sure if the intermatic is quite the same as the Muller. The Muller can be programmed for different locations and is a 365 day timer (it knows the sunrise and sunset for each day of the year at a particular spot on the earth)

but my idea is to start the motor drive at sunrise then stop it at sun set

The tricky bit, as I see it, is to have the tracking time match the hours of sunlight (about 9 hours Dec 21 to about 15 hours June 21 up here in da north)I think I can do this by varying the speed of the drive (maybe with a manual change a few times a year) or if using a linear actuator, connecting the driver to a longer pivot arm for longer days

I did not see a rating for contact voltages. The Intermatic has a 35vdc rating and I use it for exterior lighting. How would you control 2 axis?

Not sure if the intermatic is quite the same as the Muller. The Muller can be programmed for different locations and is a 365 day timer (it knows the sunrise and sunset for each day of the year at a particular spot on the earth)

This how the intermatic works and it has a DC rating!!

but my idea is to start the motor drive at sunrise then stop it at sun set

The tricky bit, as I see it, is to have the tracking time match the hours of sunlight (about 9 hours Dec 21 to about 15 hours June 21 up here in da north)I think I can do this by varying the speed of the drive (maybe with a manual change a few times a year) or if using a linear actuator, connecting the driver to a longer pivot arm for longer days

And this is the problem and always has been. A small array is alot of work to R&D but a big array 125 Sq. ft. and up is typically very robust and the gear drive motor interface is well over 125 pounds. The motor is usually just pulsed 24vdc. Google Redrock solar trackers and he will have alot of info. I have zero problems with the Wattsun trackers I have installed and use. They have some good info also. Google Array technology.

I did not see a rating for contact voltages. The Intermatic has a 35vdc rating and I use it for exterior lighting. How would you control 2 axis?

More panels beats tracking in all ways except one, if you don't have the space for the extra panels then maybe a tracker might be a solution. But frankly if you have space for a tracker its hard to imagine you couldn't have more panels

Tracking doesn't give 30-40% improvement year round, summer is best with long days and larger arc of the sun ... but that typically not when offgrid needs extra power as typically they design for worst case which in the cold, short winter months

With panels now well under 3 bucks a watt, its cheaper, no maintenance and year round power improvement to have more panels than less with a tracker.

Totally agree! I've built my own tracker for a 1700w solar array (10X170W panels) and to be fair, here in Spain in the summer, I do get about 35-40% more power and the tracker cost me about the price of one panel. This made sense at the time as I paid £4.00 per watt for the panels. But now, in the UK, I can buy panels at 50 pence per watt, so the advantage is greatly reduced even if you build your own tracker and to buy one makes no financial sense at all. (tracker manufacturers take note!).